Today, fiber delay lines (FDLs) are used to provide optical buffering in many applications, such as optical switching applications. For example, in optical packet switching delaying of optical packets is typically required, as part of traffic engineering, in order to resolve bandwidth contention.
However, existing FDLs typically provide only limited delays for optical signals. Therefore, techniques and apparatus that can be used to provide extended delays for optical signals are considered as highly desired.
Some aspects of technologies and related art that may be useful in understanding the present invention are described in the following publications:
an article entitled “Architectural and Technological Issues for Future Optical Internet Networks”, by Listanti et al in IEEE Communications Magazine, September 2000, pages 82–92;
an article entitled “IP Over Optical Networks: Architectural Aspects”, by Rajagopalan et al in IEEE Communications Magazine, September 2000, pages 94–102;
an article entitled “Labeled Optical Burst Switching for IP-over-WDM Integration”, by Chunming Qiao in IEEE Communications Magazine, September 2000, pages 104–114;
an article entitled “Approaches to Optical Internet Packet Switching”, by Hunter et al in IEEE Communications Magazine, September 2000, pages 116–122;
an article entitled “A framework for unified traffic engineering in IP over WDM networks”, by Song et al in Optical Networks Magazine, November/December 2001, pages 28–33;
an article entitled “Optimization of wavelength allocation in WDM optical buffers”, by Callegati et al in Optical Networks Magazine, November/December 2001, pages 66–72;
an article entitled “Mining the Optical Bandwidth for a Terabit per Second”, by Alan Eli Willner in IEEE Spectrum, April 1997, pages 32–41;
an article entitled “Variable optical delay line with diffraction-limited autoalignment” by Klovekorn et al in Applied Optics, Vol. 37, No. 10, Apr. 1, 1998, pages 1903–1904;
an article entitled “Picosecond-Accuracy All-Optical Bit Phase Sensing Using a Nonlinear Optical Loop Mirror”, by Hall et al in IEEE Photonics Technology Letters, Vol. 7, No. 8, August 1995, pages 935–937;
an article entitled “An Ultrafast Variable Optical Delay Technique”, by Hall et al in IEEE Photonics Technology Letters, Vol. 12, No. 2, February 2000, pages 208–210;
an article entitled “Design and Cost Performance of the Multistage WDM-PON Access Networks”, by Maier et al in Journal of Lightwave Technology, Vol. 18, No. 2, February 2000, pages 125–143;
an article entitled “Multistage Amplifier Provides Gain Across 80 nm”, by Kristin Lewotesky in Laser Focus World, September 1997, pages 22–24;
a conference review entitled “Optical amplifiers revolutionize communications”, by Gary T. Forrest in Laser Focus World, September 1998, pages 28–32;
an article entitled “Optical Networks Seek Reconfigurable Add/Drop Options”, by Hector E. Escobar in Photonics Spectra, December 1998, pages 163–167;
an article entitled “Multiple Wavelengths Exploit Fiber Capacity”, by Eric J. Lemer in Laser Focus World, July 1997, pages 119–125;
an article entitled “Advances in Dense WDM Push Diode-Laser Design”, by Diana Zankowsky in Laser Focus World, August 1997, pages 167–172;
an article entitled “Optical switching promises cure for telecommunications logjam”, by Jeff Hecht in Laser Focus World, September 1998, pages 69–72;
an article entitled “Speed Demons: Is ‘Faster’ Better and Cheaper?”, by Stephanie A. Weiss in Photonics Spectra, February 1999, pages 96–102;
an article entitled “Wavelength Lockers Keep Lasers in Line”, by Ed Miskovic in Photonics Spectra, February 1999, pages 104–110;
an article entitled “Multigigabit Networks: The Challenge”, by Rolland et al in IEEE LTS, May 1992, pages 16–26;
an article entitled “Direct Detection Lightwave Systems: Why Pay More?”, by Green et al in IEEE LCS, November 1990, pages 36–49;
an article entitled “Photonics in Switching”, by H. Scott Hinton in IEEE LTS, August 1992, pages 26–35;
an article entitled “Fiber amplifiers expand network capacities”, by Eric J. Lemer in Laser Focus World, August 1997, pages 85–96;
an article entitled “Technologies for Local-Access Fibering”, by Yukou Mochida in IEEE Communications Magazine, February 1994, pages 64–73;
an article entitled “Wavelength-Division Switching Technology in Photonic Switching Systems”, by Suzuki et al in IEEE International Conference on Communications ICC '90, pages 1125–1129;
an article entitled “Photonic Switches: Fast, but Functional?”, by Daniel C. McCarthy in Photonics Spectra, March 2001, pages 140–150;
an article entitled “Combining gratings and filters reduces WDM channel spacing”, by Pan et al in Optoelectronics World, September 1998, pages S11–S17;
an article entitled “100-Gbit/s bitwise logic”, by Hall et al in Optics Letters, Vol. 23, No. 16, Aug. 15, 1998, pages 1271–1273;
an article entitled “Analysis and Dimensioning of Switchless Networks for Single-Layer Optical Architecture”, by Binetti et al in Journal of Lightwave Technology, Vol. 18, No. 2, February 2000, pages 144–153;
an article entitled “Fiber-based components meet the needs of next-generation amplifiers”, by Stephane Bourgeois in WDM Solutions, March 2001, pages 67–74;
an article entitled “Keep Your Photons in Line”, by Wesson et al in Photonics Spectra, September 1999, pages 102–108;
an article entitled “Photons At Work: Optical Networks On The Rise”, by Lee Goldberg in Electronic Design, Mar. 22, 1999, pages 56–66;
an article entitled “Photonic packet switching and optical label swapping”, by Daniel J. Blumenthal in Optical Networks Magazine, November/December 2001, pages 54–65;
an article entitled “On a dynamic wavelength assignment algorithm for wavelength routed all-optical networks”, by Stoica et al in Optical Networks Magazine, January/February 2002, pages 68–80;
an article entitled “Crystal slows and stops light”, by John Wallace in Laser Focus World, February 2002, Vol. 38, No. 2, pages 36–37;
an article entitled “Decision feedback loop compensates at 10 Gbit/s”, by Hassaun Jones-Bey in Laser Focus World, May 2000, pages 65–67;
an article entitled “100-km Negative-Dispersion Fiber carries 10 Gb/s”, by Richard Gaughan in Photonics Spectra, November 2001, page 42;
an article entitled “Managing Polarization Mode Dispersion”, by Michel W. Chbat in Photonics Spectra, June 2000, pages 100–104;
an item entitled “Alcatel Displays 1.6-Tb/s Transmission” in the Presstime Bulletin section in Photonics Spectra, December 2001, page 18;
an article entitled “Dynamic Dispersion Compensation: When and Where Will It Be Needed?”, by Lisa Huff and Christine Mulrooney in Photonics Spectra, December 2001, pages 122–125;
an article entitled “Dispersion management is vital for high-speed systems”, by Jeff Hecht in Laser Focus World, July 2001, pages 79–87;
an article entitled “Tunable compensators master chromatic-dispersion impairments”, by Alan Willner in WDM Solutions, July 2001, pages 51–58;
an article entitled “Dispersion Compensation Gratings for the C-Band”, by James F. Brennan III in Photonics Spectra, June 2001, pages 159–165;
a newsbreak item entitled “Hot rubidium slows light speed to 90 m/s”, in Laser Focus World, August 1999, page 11;
a newsbreak item entitled “Network demonstrates 1500-km unregenerated transmission at 40 Gbits/s”, in Laser Focus World, July 2001, page 11;
an article entitled “Electroholographic switches are fast and compact”, by Aharon J. Agranat in Laser Focus World, May 2001, pages 109–112;
a newsbreak item entitled “Switch based on SOA achieves femtosecond switching”, in Laser Focus World, September 2001, page 9;
an article entitled “Next-generation networks may benefit from SOAs”, by Martin Young in Laser Focus World, September 2001, pages 73–79;
an article entitled “All-optical converters promise improved networks”, by Jeff Hecht in Laser Focus World, April 2001, pages 159–164;
an article entitled “Novel VOAs provide more speed and utility”, by Stephen Cohen in Laser Focus World, November 2000, pages 139–146;
an article entitled “Array-based VOAs offer compact signal control”, by Nigel Cockroft in WDM Solutions, June 2001, pages 81–86; and
The following chapters in The Communications Handbook, CRC Press & IEEE Press, 1997, Editor-in-Chief Jerry D. Gibson: Chapter 39 on pages 542–553; and Chapter 65 on pages 883–890.
Additional aspects of technologies that may be useful in understanding the present invention are described in the following patents and patent applications:
U.S. Pat. No. 4,626,075 to Chemla that describes a nonlinear optical device that includes a layered semiconductor structure having layers of different energy band gap materials;
U.S. Pat. No. 5,191,457 to Yamazaki that describes a WDM optical communication network in which optical beams are modulated by channel discrimination signals of different frequencies;
U.S. Pat. No. 5,774,244 to Tandon et al. that describes an optical communications network that includes a plurality of passive optical networks (PONs) connected in a ring in PON address order, in which communication channels between terminals are wavelength multiplexed;
U.S. Pat. No. 6,233,082 to Johnson that describes an optical transmitter for generating any one of N carrier signals for use in an M-channel WDM system;
U.S. patent application Ser. No. 09/126,378 of Handelman, now U.S. Pat. No. 6,404,522, that describes improvements in communication performance of an optical communication system that communicates data via N different channel wavelengths using WDM;
U.S. patent application Ser. No. 09/389,345 of Handelman, now U.S. Pat. No. 6,574,018, that describes a network control system that may be embodied in various elements of a communication network that communicates optical signals multiplexed by WDM, where the network control system may limit a number of channel wavelengths actually used for communicating optical signals to an end node, and control and modify data rates carried over channel wavelengths multiplexed by WDM;
U.S. patent application Ser. No. 09/624,983 of Handelman, now U.S. Pat. No. 6,763,191, that describes an optical switching apparatus that selectively combines and separates series of optical signal samples using OTDM and/or WDM;
Published U.S. patent application Pub. No. U.S. 2002/0048067 A1 of Handelman et al that describes an optical switching apparatus that selectively combines and separates, using OTDM and/or WDM, optical signal samples that are obtained by a spread spectrum technique or a combination of optical signal samples that are obtained by a spread spectrum technique and optical signal samples that are carried over discrete channel wavelengths;
U.S. patent application Ser. No. 09/944,603 of Handelman, now published as Pub. No. US 2003/0048506, that describes an optical packet switch that switches optical packets according to bit-rates at which the optical packets are provided; and
U.S. patent application Ser. No. 10/057,991 of Handelman, now published as Pub. No. U.S. 2003/0043430, that describes an optical packet switch in which NW wavelengths, over which inputted optical packets may be switched, are grouped into KG groups of wavelengths, where the KG groups of wavelengths are characterized in that each of the KG groups of wavelengths is allocated to optical packets distinguished from other optical packets by at least one attribute of at least one packet characteristic, and each one inputted optical packet is switched over a wavelength having an available transmission resource selected from among wavelengths in one of the KG groups of wavelengths that is matched to the one inputted optical packet by correspondence of attributes of the at least one packet characteristic.
The disclosures of all references mentioned above and throughout the present specification are hereby incorporated herein by reference.